I have about 50 repositories. It would cost me a lot per month to host it on Github. Why do I want to use Github? Because I'm transitioning from C# (MVC3) work to Ruby on Rails work.
Heroku only integrates well with Github (for some stupid reason) and I would prefer to host it on Github for my comfort.
I'm located in Bolivia. I do not charge 4000$ per project. My cost of living is lower, hence, my rates are lower than most first world country programmers. There's your reason why I can't afford Github's ridiculous prices.